The only reasons I can think of for going with readymix and a pump are better quality and lower cost.   If you pour a cement mixer worth of concrete down the ICF forms, then pour the next batch next to the first, etc., by the time you get around to the starting point, you'll have two problems.  Actually, three problems if you have a county inspector, architect, or other quality control person on site.  They would shut you down.

1) Cold joints.  Unless you're back around in 45 minutes or less, depending on the mixture and temperature, your going to have cold joints.  Not a problem if strength, longevity, and water resistance aren't an issue for you.  Remember, no stopping all the way to the top.  I've seen several retaining walls and partial basements poured this way with great success, but it took several guys humping from sun-up to sun-down.  Can't imagine doing a single story ICF of more than about 450 square feet and only then if the mixer is somehow higher than the wall.

2)  Air pockets.  When you get back around to your starting point, even if there is no cold joint, it's very likely that gobs of concrete will have landed and solidified on the rebar, tie wires, support benches, etc.  Now, you're going to be trying to fill underneath all of the obstructions this method creates.  Not good.  You coat the first gobs on the second go-around, so they can be fairly large on a tall wall.

As to cost, I don't see the savings.  Buying bags of concrete can't possibly compete with delivery, even if you can get the bags delivered free and placed right where you want them.  Every time you pick up a bag, even if only to lift up the the mixer, you'll say to yourself "why didn't I just pay for readymix and get it over with."  Be sure to calculate how many times you'll say that to yourself before you decide to use bags.  If you get to use a wheelbarrow, you'll say it even more times and with some cursing.  Bags are for jobs less than a yard and farther than 50 miles from the plant.

Mark Fleming

Last time I saw a wall hinge failure was the Nisqually quake in Seattle.  Surprised you missed that.  There were several of them. 

There's a great study of reinforced concrete wall failures that used to be available on the web.  They had great names for the types of failures ("double-hinge pancake" was my favorite).  I think it was a HUD study, but I know that one of the sponsors was a search and rescue organization, because they tend to go into the crumpled buildings.  I may still have a link to the site somewhere.  I printed out a hard copy, but it would even be more difficult to find in my files.

I'm not saying that every wall with cold joints will fail.  Some, like you point out, have been around for years.  Most, as you didn't point out, could not be built today because of code standards. 

Anyone trying to save money by using bags, be sure to tell your architect that you're going to pour from inconsistant bag mixes in 145 lifts over 7 days.  My guess is that the design and rebar schedule will change dramatically (assuming that the architect doesn't quit).  There go the cost savings.

Mark